An organic light-emitting device is an electronic device in which a thin film containing a fluorescent organic compound or a phosphorescent organic compound is sandwiched between an anode and a cathode. In the organic light-emitting device, a hole (positive hole) and an electron are injected into the thin film containing the fluorescent organic compound or the phosphorescent organic compound from the electrodes. When the hole and the electron are recombined with each other in the thin film, an exciton of the fluorescent organic compound or the phosphorescent organic compound is produced. When this exciton returns to its ground state, the organic light-emitting device emits light.
The recent organic light-emitting device has remarkably advanced, and makes it possible to produce a thin and lightweight organic light-emitting device which has high brightness at low applied voltage, various emission wavelengths and high speed response. Thus, the organic light-emitting device has a possibility that it can be employed for wide-ranging applications.
However, under the present conditions, the organic light-emitting device needs to acquire a light output with higher brightness or higher conversion efficiency. In addition, the organic light-emitting device still has many problems in durability. For example, the device undergoes changes over time associated with its long-term use or is degraded by atmospheric gas containing oxygen, humidity and the like. Furthermore, the organic light-emitting device needs to emit lights of blue, green and red having high color purity when the device is applied to a full color display or the like. However, the organic light-emitting device in which these problems have been sufficiently solved has not been provided.
A method of employing a dibenzo[c,g]fluorene compound as a material constituting an organic light-emitting device is proposed so as to solve the afore-mentioned problems. The examples of the dibenzo[c,g]fluorene compound and the organic light-emitting device using same are disclosed in WO 2003/051092, US 2004/0131880, and Synthesis, photophysics and electroluminescence of poly(dibenzofluorene)s (Wei-Zhi Wang et al. Macromolecular Rapid Communications, Vol. 27, No. 14, p. 1142 (2006)). WO 2003/051092 discloses a compound which is substituted with a hole-transporting heterocyclic group such as an oxadiazole group, a thiadiazole group, a triazole group, a diarylamine group and a carbazole group at the 5- and 9-positions of the skeleton of a dibenzo[c,g]fluorene.
In addition, US 2004/0131880 discloses a compound which is substituted with a heterocyclic group such as thiophene and carbazole at the 5- and 9-positions of the skeleton of a dibenzo[c,g]fluorene.